100 mph in a TJ; have you done it?

[aston4]

I did it once. Once. Indicated, not GPS, but my speedo is spot on at lower speeds, with 235 tires, so I think it was a real 100mph.

6cyl, 5 speed, ‘97, bone stock.

Engine and drive train were loafing, it’s a tall 5th gear. Hard top was on.

I would describe the overall feel as “mildly terrifying.” I didn’t feel like I was just about to crash and burn, but rather it was a definite possibility. My TJ cruises comfortably at 85, so it wasn’t all that much faster, but I’ll never do it again. Just wanted to see if it could.

I feel like I probably would have topped out around 110-115 drag limited, but the speedo doesn’t go that high anyway.

Has anyone gone faster?

 

[rasband]

At least in the later models, the governor kicks in in the mid 90s. I've only ever maxed to that (and even down hill that was pretty much it). But I can comfortably go 80 on the way to Moab without white knuckling.

 

[aston4]

At least in the later models, the governor kicks in in the mid 90s. I've only ever maxed to that (and even down hill that was pretty much it). But I can comfortably go 80 on the way to Moab without white knuckling.

Huh. No sign of a governor on my '97. I have two other cars with governors, 110 and... I think 128. The 110 is a Toyota minivan and could probably easily go into the 130s, the 128 when flashed away would do a little over 150 according to YouTube, but that's Autobahn stuff, I have no interest, and don't feel like going to jail.

People around here regularly push well into triple digits in clapped out pickups on the regular. I mostly drive like Grandma.

 

[ColoJeep]

I ran my 99 up to 95+ m.p.h once , it took a little bit of time at 6500 ft. elevation. , the TJ was a little twitchy but it sounded like a B -17 in a 70 Degree dive , balls to the wall. There is a reason God let us invent road cars .

 

[aston4]

I ran my 99 up to 95+ m.p.h once , it took a little bit of time at 6500 ft. elevation. , the TJ was a little twitchy but it sounded like a B -17 in a 70 Degree dive , balls to the wall. There is a reason God let us invent road cars .

Yeah TJs ain't quiet. I'd describe it more like an old overheating tractor noise, not the beautiful air-cooled radial sound.

 

[Cooper Smith]

I did it once. Once. Indicated, not GPS, but my speedo is spot on at lower speeds, with 235 tires, so I think it was a real 100mph.

6cyl, 5 speed, ‘97, bone stock.

Engine and drive train were loafing, it’s a tall 5th gear. Hard top was on.

I would describe the overall feel as “mildly terrifying.” I didn’t feel like I was just about to crash and burn, but rather it was a definite possibility. My TJ cruises comfortably at 85, so it wasn’t all that much faster, but I’ll never do it again. Just wanted to see if it could.

I feel like I probably would have topped out around 110-115 drag limited, but the speedo doesn’t go that high anyway.

Has anyone gone faster?

No and there's a good reason why I didn't.

 

[aston4]

No and there's a good reason why I didn't.

 

[Steel City 06]

100+ is fairly easy to hit if you're not paying attention, especially passing on a 2-lane road and the other person speeds up. Once you hit about 100, the steering tends to get fairly twitchy. That said, in my experience the tires/suspension ride smooth like glass above 95.

I'm on the ubiquitous 35s and 5" of lift, stock 4.10 gears. 6th gear will allow you to hold 100 on flat ground, but if you're trying to go 110+ or hold 100+ with any real slope and 5th is needed.

 

[jjvw]

I did it once. Once. Indicated, not GPS, but my speedo is spot on at lower speeds, with 235 tires, so I think it was a real 100mph.

6cyl, 5 speed, ‘97, bone stock.

Engine and drive train were loafing, it’s a tall 5th gear. Hard top was on.

I would describe the overall feel as “mildly terrifying.” I didn’t feel like I was just about to crash and burn, but rather it was a definite possibility. My TJ cruises comfortably at 85, so it wasn’t all that much faster, but I’ll never do it again. Just wanted to see if it could.

I feel like I probably would have topped out around 110-115 drag limited, but the speedo doesn’t go that high anyway.

Has anyone gone faster?

Years ago on 33s, I made it to about 98mph on GPS. It was just noisy from wind.

 

[Zataxx]

Yes and I thought my Tj was gonna fall apart from it.

 

[Cooper Smith]

100+ is fairly easy to hit if you're not paying attention, especially passing on a 2-lane road and the other person speeds up. Once you hit about 100, the steering tends to get fairly twitchy. That said, in my experience it rides smooth like glass above 95.

I'm on the ubiquitous 35s and 5" of lift, stock 4.10 gears. 6th gear will allow you to hold 100 on flat ground, but if you're trying to go 110+ or hold 100+ with any real slope and 5th is needed.

I literally needed a tailwind and a steep downward slope just to hit 70 mph in mine.

 

[aston4]

I wonder if the TJ has higher top speed at high altitude. I felt like it had a lot more to go, engine wise, at 100. But it was at 7200ft. I know the 4.0 is supposedly a lot less powerful at higher altitude, but I think wind drag probably matters more than decreased engine power.


ETA: I think the air is 30% or so less dense at 7000ft?

 

[jjvw]

I wonder if the TJ has higher top speed at high altitude. I felt like it had a lot more to go, engine wise, at 100. But it was at 7200ft. I know the 4.0 is supposedly a lot less powerful at higher altitude, but I think wind drag probably matters more than decreased engine power.

Transmission, axle gearing, and tire size are what make the difference.

 

[aston4]

Transmission, axle gearing, and tire size are what make the difference.

I have no idea what my ratios are in my stock '97, but 5th gear is so tall it is much more comfortable at 80mph than 60mph. At 60 I have to constantly downshift to maintain speed even at moderate upslopes.

 

[Cooper Smith]

I have no idea what my ratios are in my stock '97, but 5th gear is so tall it is much more comfortable at 80mph than 60mph. At 60 I have to constantly downshift to maintain speed even at moderate upslopes.

What's your rpm in 5th at 80 mph? Be precise.

 

[Steel City 06]

Transmission, axle gearing, and tire size are what make the difference.

Yup. Ideally you want a to be in a gear that pulls around 4,500 to 5,000 RPM at your top speed. In my case, that's 5th gear. The goal is maximum engine power.

Interestingly, given the cube ratio of power required versus speed, if you add a supercharger onto a TJ that doubles your horsepower from say 200 HP to 400 HP, your top speed only goes from about 110 mph to 129 mph, assuming you e geared correctly in both cases.

 

[jjvw]

What's your rpm in 5th at 80 mph? Be precise.

And be more precise on the tire size. 235mm is the tread width.

 

[aston4]

What's your rpm in 5th at 80 mph? Be precise.

I think around 2500? Maybe 2600. I don't remember exactly now. I moved a hundred miles from the nearest interstate now and rarely get above 65. I think it is about exactly 2000 at 70mph.

 

[aston4]

And be more precise on the tire size. 235mm is the tread width.

lol okim dum lol

eta: 235 75 15? whatever stock is.

 

[suicideking]

06 with auto 42RLE, 37's, 5.38 gears. I usually set the cruise control to 70mph. I won't intentionally go above 75.